Category: Research Article Co-Occurrence of Lutzia Fuscana

Volume- 5 ISSN: 2362-0080 Issue- II Rajarata University Journal December-2020 www.ruj.ac.lk/journals/

Category: Research Article

Co-occurrence of Lutzia fuscana and Aedes albopictus (Diptera: Culicidae) in Native Habitats: as an Implication for Biological Control

*1Dissanayake Dinithi & 2Wegiriya Hemantha *1 The office of the Regional Director of Health Services, Galle, Sri Lanka 2 Department of Zoology, Faculty of Science, University of Ruhuna, Matara, Sri Lanka

ARTICLE DETAILS ABSTRACT Article History The larval stages of Lutzia fuscana are predators and feed on larvae Published Online: of other mosquito species. The present study aimed to investigate the 30th December 2020

co-occurrence of L. fuscana and Aedes albopictus in Thitthagalla in the Imaduwa Pradeshiyasaba area which is in the Galle District of the Keywords Container Index, Natural predation, Southern Province of Sri Lanka. As the mean of number L. fuscana Mosquito larval stages larvae per cement container increased, there was a significant reduction in the mean number of Ae. albopictus larvae per cement container (- *Corresponding Author 0.619, P<0.01). There was no significant correlation between the mean numbers of Ae. albopictus pupae per cement container per week and [email protected] the mean number of L. fuscana larvae per cement per week. L. fuscana larvae per cement container per week showed a positive linear correlation with temperature (Pearson correlation= 0.713, P<0.01), a negative linear correlation with relative humidity (Pearson correlation = - 0.419, P<0.01) and no linear correlation with the rainfall (Pearson correlation=-0.200, P>0.05). Container indices (% of positive containers) of 50% and 32% for L. fuscana were recorded for water storage cement tanks and tyres respectively, and for Ae. Albopictus larvae 50% and 72% were respective container index values.

1. Introduction

Biological control of mosquitoes using natural and tubificid worms [9], making them a potential as predators is presently getting promoted due to its biological control agent of different mosquito least effect to the ecosystem function and species species [4, 5, 10, 11,12]. However, little effort by assemblages. Vector borne disease transmission Singh et al. [5] has been made to evaluate their can be reduced successfully by measures against predatory potential to promote them as biological the vectors, especially in mosquitoes [1]. Interaction control agent against the vector mosquitoes that between the natural predators and mosquitoes is a thrive in small mosquito larval habitats. In view of part of relationship among the community members this, an attempt was made to assess the potential of at large [2]. Predators of mosquito are found in L. fuscana larvae as a biological control measure diverse numbers in large mosquito larval habitats against the dengue vector Ae. albopictus (Diptera: [3] in contrast to the smaller larval habitats. Culicidae) under natural field conditions. As one of the few predators [3] that are common In view of the expansion of geographic range of in the smaller mosquito larval habitats, the larval the vector, it is possible that the role of Ae. stages of the mosquito Lutzia fuscana (Diptera: albopictus in the transmission of Dengue and Culicidae) [2, 4, 5] are common to abundant in a chikungunya will increase [13]. Previous studies variety of mosquito larval habitats in India, Sri have indicated that Ae. albopictus occur in greater Lanka, Thailand and Pakistan. Recent taxonomic abundance than Ae. aegypti in several areas of Sri studies [6] have led to the elevation of subgenus Lanka that have experienced outbreaks of Dengue Lutzia to the genus level; hence the erstwhile name in the past [14]. of Culex fuscanus is presently replaced as L. The present study was carried out to determine fuscana. the co-occurrence of L. fuscana and Ae. albopictus The larval stages of L. fuscana are aquatic in their native habitats, the breeding site of L. predators that feed on the larvae of other mosquito fuscana and Ae. albopictus and the correlations of species [5, 7, 8] as well as the chironomid larvae L. fuscana population with climatic factors.

© RUJ 2020, All Rights Reserved Page 52 Co-occurrence of mosquito larvae for biological control Volume-5, Issue II, December-2020 Rajarata University Journal 2. Material and Methods applied to test for significant correlation between mean Ae. albopictus and L. fuscana larvae per A preliminary study was conducted in December cement container. Pearson correlation was applied 2016 prior to the present study. Factors such as to test for significant correlation between the mean past entomological data, environmental conditions, number of L. fuscana larvae per cement container availability of breeding sites, and feasibility of field per week with the temperature, relative humidity operations to collect relevant data were considered and rainfall. in selecting study areas. The present study was carried out at 3. Results Thitthagalla (Longitudes 800.22’ and Latitudes 60.03’) in the Imaduwa Pradeshiyasaba area which 3.1 Container index values is in the Galle District of the Southern Province of The types of containers surveyed and number Sri Lanka mainly termed as a rural setting with large of positive containers for Ae. albopictus and for L. trees and other vegetation surrounding human fuscana larvae are shown in Table 1. In addition, habitations. The selected site is approximately 2km the results of container index are mentioned. The in an area bounded by Paddy fields. The study was main inspected container type was discarded conducted regularly throughout January 2017 to receptacles. As such the most positive container December 2017. type was also discarded receptacles. Among other A total of 10 cement containers sized with 25 cm types of containers, clay pots and tires were ×25 cm × 5 cm filled with 1000 ml of water were commonly inspected and also highly positive. placed in ten selected outdoor stations 100 m apart. Discarded receptacles and clay pots were highly The number of Aedes and Lutzia larvae were positive for Ae. albopictus larvae, whereas tires recorded at the end of each week, after which the were commonly positive for L. fuscana larvae water was discarded and the containers were (Table 1). refilled with water. Preliminary identification in the In the collection of outdoor potential breeding field was done by visually examining the larvae sites all the collected Aedes larvae were Ae. during collection; species identification was albopictus and all the collected Lutzia larvae were confirmed in the laboratory, using standard keys L. fuscana. [15, 16]. Discarded receptacles (93%), overhead tanks A preliminary survey identifying all potential (75%) and Tires (72%) showed high CI value for breeding habitats such as domestic and peri- Ae. albopictus larvae. The CI values of L. fuscana in domestic water storage containers, cement tanks, the above containers were 5%,25% and 32% ponds, ditches and overhead tanks, in 100 respectively. The CI values of water storage cement premises was conducted for a period of one month tanks were 50% for both larval species. Whereas, in prior to the research study. Ae. albopictus and L. the view of biological control, it could be clearly fuscana species were examined for their larval seen that container indices for Ae. albopictus got breeding and 10 mature 4th instars larvae from each increased comparatively with the decreasing of CI container were randomly collected in separate values for L. fuscana (Table 01). containers and identified in the laboratory using standard keys [15, 16].If a container had less than 3.2 The occurrence of Ae. albopictus 10 larvae, all larvae were collected [17]. Pipetting, larvae,pupae and L. fuscana larvae siphoning and dipping techniques were used for collecting larvae depending on the nature of the The mean number of Ae. albopictus larvae in breeding habitat. The percentage of positive cement containers fluctuated significantly week to containers for Ae. albopictus and L. fuscana is week. In the same cement tank, the mean number termed as Container Index (CI). of L. fuscana larvae did not vary much in general, but the mean number of L. fuscana larvae Rainfall, temperature and relative humidity data increased during the weeks 2, 13 and 17, and for the study area were obtained from the interestingly, the mean number of Ae. albopictus Meteorological Department, Sri Lanka. larvae reduced significantly. However, the mean The data was analyzed by using SPSS statistical number of Ae. albopictus pupae did not vary software version 20. Pearson correlation was significantly (Figure 1).

Table 1: Breeding site preferences and container Index values of Ae. albopictus larvae and L. fuscana larvae in Thittagalla area in Galle district

No. of No. of Positive for Positive for CI for CI for inspected positive Ae. albopictus L. fuscana Ae. albopictus L. fuscana Container type containers containers larvae larvae larvae larvae

Water storage cement tanks(already within the area) 8 5 4 4 50% 50% Clay pots 29 20 20 4 68.96% 13.79% Ponds 19 8 7 4 36.84% 21.05% Overhead tanks 12 9 9 3 75% 25% Tires 25 22 18 8 72% 32% Natural habitats 15 9 9 1 60% 6.67% Discarded receptacles 43 40 40 2 93% 5%

100

80 Mean no.of Lutzia 70 fuscanus larvae per cement container per 60 week

50 Mean no.of Aedes albopictus larvae per 40 cement container per

No. of individuals per container individuals per cementof No. week 30 Mean no.of Aedes 20 albopictus pupae per 10 cement container per week 0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 Week

Figure 1: Mean number of Ae. albopictus larvae, pupae and L. fuscana larvae per cement container per week 3.3 The relationship of L. fuscana larvae with larvae per cement container per week was not Ae. albopictus larvae, and pupae and with significantly correlated (Figure 3). environmental factors The mean number of L. fuscana larvae per The number of Ae. albopictus larvae reduced cement container showed a significant positive significantly with increasing number of L. fuscana linear correlation with the temperature (Pearson larvae per cement container. (Pearson correlation of correlation= 0.713, P<0.01) (Figure 4). mean Ae. albopictus larvae per cement container Mean number of L. fuscana larvae per cement and mean L. fuscana larvae per cement container container showed a significantly negative linear were -0.619, P<0.01 (Figure 2). correlation with relative humidity (Pearson The number of Ae, albopictus pupae per cement correlation = -0.419, P<0.01) (Figure 5). container per week with the number of L. fuscana

Figure 6: Mean number of L. fuscana larvae Figure 2: Mean number of L. fuscana larvae per per cement container per week with the cement container per week with the mean Rainfall number of Ae. albopictus larvae per cement container per week There was no linear correlation between the mean number of L. fuscana larvae per cement container per week with the rainfall (Pearson correlation=-0.200, P>0.05 (Figure 6).

4. Discussion

There have been several reports on predatory and feeding behavior of L. fuscana [5, 9]. These behaviours were studied in laboratory conditions. Figure 3: Mean number of L. fuscana larvae per Currently, there is a lack of studies conducted in the cement container per week with the mean natural environment. This study attempted to number of Ae. albopictus pupae per cement investigate the breeding potential of L. fuscana on container per week Ae. albopictus in outdoor natural environment. According to the present study, all Aedes larvae found in the study site, including the outdoor potential breeding habitats were Ae. albopictus and all Lutzia larvae were L. fuscana. This is mainly due to the environmental factors. The study area was in a rural setting of large trees with tree holes, covered leaf axils and other vegetation surrounding the area, which are known natural breeding sites of Ae. albopictus and L. fuscana. The number of Ae. albopictus larvae per cement container per week

Figure 4: Mean number of L. fuscana larvae per were significantly reduced with the increasing cement container per week with the temperature number of predatory larvae L. fuscana. This is probably due to the prey-predator relationship of the two species. However, as there was no significant correlation between the Ae. albopictus pupae and the L. fuscana larvae, it may be the L. fuscana are able to fulfill the food requirement with the higher abundance of Ae. albopictus larvae. According to the Singh et al [4], the breeding temperature of the predatory mosquito L. fuscana were at 18 0C–34 oC and contained some decaying leaf debris from the trees. Our study also showed that the mean number of L. fuscana increased with 0 0 Figure 5: Mean number of L. fuscana larvae per the temperature between 28 C-33 C. Singh et al cement container per week with the relative [4], reported that the optimum relative humidity for humidity breeding in the laboratory condition is about 60-70 RH. In this study the number of L. fuscana increased with relative humidity and the range

© RUJ 2020, All Rights Reserved Page 55 Dissanayake and Wegiriya Co-occurrence of mosquito larvae for biological control Volume-5, Issue II, December-2020 Rajarata University Journal between 70-90 RH at the field. Low rainfall has Acknowledgement previously been stated to reduce the breeding in L. We would like to thank all field supporters for fuscana [4]. Within our study, there was no their kind help in collecting various information and correlation between the number of L. fuscana and to Meteorology Department, Sri Lanka, for providing the rainfall. The result may be due to the fact that rainfall data for the study. the area has no specific rainfall fluctuations throughout the year.

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